US3208219A

US3208219A - Hydraulic system for dies

Info

Publication number: US3208219A
Application number: US354700A
Authority: US
Inventors: Floyd M Williamson
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-03-25
Filing date: 1964-03-25
Publication date: 1965-09-28
Anticipated expiration: 1982-09-28

Description

Sept. 28, 1965 F. M. WILLIAMSON HYDRAULIC SYSTEM FOR DIES 2 Sheets-Sheet 1 Filed March 25, 1964 INVENTOR. 722 1.47 M7Z 'd27aswz Sept. 28, 1965 F. M. WILLIAMSON 3,208,219

HYDRAULIC SYSTEM FOR DIES Filed March 25, 1964 2 Sheets-Sheet 2 1 N VEN TOR.

f/ay] M 1447Za27ns071.

United States Patent "ice 3,208,219 HYDRAULIC SYSTEM FOR DIES Floyd M. Williamson, 2405 E. Grand Blvd., Detroit, Mich. Filed Mar. 25, 1964, Ser. No. 354,700 13 Claims. ((11. 6051) This application is a continuation-impart of my prior application Ser. No. 145,297, filed Oct. 16, 1961, for Hydraulic Control for Dies in Ram Type Presses; Ser. No. 250,444, filed Jan, 9, 1963, for Hydraulic System for Dies; Ser. No. 231,131, filed Oct. 17, 1962, now Patent No. 3,163,144 issued Dec. 29, 1964, for Hydraulic Cushions for Dies of Ram Type Presses; and Ser. No. 863,315, filed Dec. 31, 1959, now forfeited, for Hydraulic System for Dies.

This invent-ion relates to hydraulic cushions for controlling the movement of dies in a press in sheet metal drawing and stamping operations, and has particular reference to systems of the type which includes a hydraulic pressure booster to provide resistance to movement of a die during closing of the press ram in a crank type press.

In systems of this type as now in use, the pressure in the hydraulic circuit suddenly rises during closing of the press ram to undesirably high levels due to the inertia of the booster pistons and the frictional resistance to movement of such pistons and the oil in the circuit in response to the closing of the press ram. This is not only dangerous because of the possibility of rupture of the hydraulic circuit, but also disadvantageous because of the inherent inability in such systems to accurately control the back pressure exerted by the die on the blank during the closing of the press ram.

This invention eliminates such difliculties and provides a simple, safe, flexible hydraulic system for controlling such dies whereby the pressure thereof may be easily and accurately controlled for forming and stripping purposes.

A principal object of the invention, therefore, is to provide a new and simplified hydraulic circuit for controlling the movement of dies in sheet metal drawing and stamping operations.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there are two sheets, which by way of illustration show preferred embodiments of the invention and what I now consider to be the best mode of applying the principles thereof.

In the drawings:

FIG. 1 is a schematic view of a system embodying the invention applied to the dies of a crank type press;

FIG. 2 is a schematic view of a press operated switch which may be employed to control the energizati-on of the high pressure cylinder; and

FIG. 3 is a schematic view of a modification of the system of FIG. 1.

As illustrated in FIG. 1, a system embodying the invention comprises a hydraulic circuit including one or more actuating cylinders 10, a tank of low pressure hydraulic fluid 12, a high pressure cylinder of an air pressure actuated hydraulic pressure booster 14, and a directional valve 16. An air valve 18 controls the cycling of the booster 14. Each cylinder is mounted on the fixed bolster 20 of a crank type reciprocating press and is provided with a piston 22 arranged to react on a die 24 in the forming of the blank 26. One or more coil springs 28 may be arranged to react on the bolster 20 and die 24 for retracting the latter against the hydraulic pressure applied to the pistons 22 by the hydraulic fluid in tank 12.

Each actuating cylinder 10 is connected by hydraulic fluid line 36 to the directional valve 16, and the valve 16 3,Z8,Zl9 Patented Sept. 28, 1965 in turn is connected by hydraulic fluid pressure line 38 to the lower end of the tank 12 whereby the cylinders 10 normally are supplied with hydraulic fluid under tank pressure. The tank 12 is charged with a suitable quantity of hydraulic fluid and in addition is supplied with air under pressure through the line 40 under the control of the regulating valve 42, whereby a predetermined pressure is maintained in the tank 12, say for example 100 lbs. per square inch. The high pressure cylinder 15 of booster 14 is connected to the valve 16 by a hydraulic fluid line 44 whereby the high pressure cylinder is also supplied with hydraulic fluid under tank pressure. The hydraulic fluid line between the tank 12 and the actuating cylinders 16 includes, in addition to the

lines

36 and 38, certain bores and passages in the valve 16, namely bore 46, port 48, valve chamber provided by the valve sleeve 50, port 52, and bore 54 so that when the valve 16 is disposed as illustrated, an open or free flow line is proided between the tank 12 and the actuating cylinders 10. The bore 54 communicates with the line 3 8 and also with a bore 56 which leads to check valve chamber 58. Bore 60 also communicates with check valve chamber 58. Ball check valve 62 biased to its seat by coil spring 64 permits the free flow of hydraulic fluid from the bore 56 through the check valve chamber 58 and into the bore 60 which communicates with the line 44 which leads to the upper end of the high pressure cylinder 15 whereby the latter is supplied with hydraulic fluid under tank pressure.

A high pressure piston 68 is disposed in the cylinder 15 and is operable when energized by the air piston 70 to discharge hydraulic fluid from the cylinder 15 into the line 44 under relatively high pressure, say, for example, 1500 lbs. per square inch. The air piston 70 operates in an air cylinder 72 which is supplied with air under pressure through line 74. The pistons 68 and 70 are interconnected so as to move together, and together with their cylinders 66 and '72 form the air pressure operated booster 14. The air is supplied to line 74 under thecontrol of a pressure regulating valve 76 whereby the maximum pressure developed in the high pressure cylinder 15 may be controlled.

A rotary valve indicated generally at 18 is adapted to control the supply of air under pressure through the line 74 and to port the line 74 to atmosphere whereby the booster 14 may be cycled. As illustrated, the rotary member of the valve 1 8 is biased to port the line 74 to atmosphere through the port 78 by spring 80 which reacts on valve arm 82. The core of the solenoid 84 is connected by link 86 to the arm 82 of the valve 18 whereby when the solenoid 84 is energized, the valve 18 will be positioned so that the line 74 will supply air under pressure to the air cylinder '72 for energizing the high pressure cylinder 15. The solenoid 84 may be controlled by a normally open switch 90 which is periodically closed by a rotary cam 92 which is geared to the crank of the press so that the switch 90 will be closed at a predetermined part of the press cycle. The cam 92 may be of such a character as to close the switch 90 momentarily or to hold it closed for some time period, depending upon the time that it is desired to have the high pressure cylinder 15 energized. The cam 92 may have more than one lobe so that the high pressure cylinder 15 will be energized more than once during each cycle of the press.

The directional valve includes the sleeve 50 which provides the valve bore having ports 48, 52, 102 and 104, port 52 communicating with bore 54 and port 48 communicating with bore 46. Port 102 communicates through bore 106 with bore 108, which in turn communicates with bore 46, while port 104 communicates with bore 60. Preferably check valve 107 is disposed between port 102 and bore 106 to prevent return flow through port 102. is reciprocable in the bore 100 and biased by the coil spring 112 to normally close the ports. 102 and 104 while leaving the ports 48 and 52 open so that the actuating cylinders are in open communication with the tank 12.

Energization of the high pressure cylinder will discharge high pressure hydraulic fluid into the line 44 and shift the valve 110 to its other position so as to open communication between the ports 102 and 104 and to block communication between the ports 48 and 52 whereby the high pressure fluid discharged from the cylinder 15 is directed through the port 102 and the bore 108 and the bore 46 and trapped in the line 36 and the cylinders 10. The high pressure cylinder 15 is energized before the closing of the press ram so that the pistons 22 will react on die 24, forcing it to its extended position so that upon closing of the press ram, die 24 will be positioned to cooperate with upper die 25 in the first drawing operation on blank 26. During this drawing operation and the closing of the press ram, the cylinder 15 is maintained energized unless release of the cushion pressure on the blank is desired. It is to be understood that the blank 26 is clamped between the die rings 27 and 29 during closing of the press ram. As the ram continues to close, die 25 carried thereby, after the initial drawing of the center of the blank, reacts on the blank and die 24 so as to perform the second draw on the blank 26, the die 24 receding and reacting on the pistons 22, which are subject to the discharge pressure of the booster 14. Such pressure provides a hydraulic cushion substantially greater than tank pressure to the displacement of die 24 during closing of the press ram.

The pressure of the hydraulic cushion depends upon the relative sizes of the pistons 68 and 70 and the pressure setting of the adjustable regulating valve 76. By way of example, the pressure generated by the booster 14 may be 1500 lbs. per square inch, or 2500 lbs. per square inch, or whatever high pressure may be desired for the drawing operation to be carried out. After the press ram closes, the booster 14 may be deenergized for a brief time sufficient to permit the ram to open, when the booster 14 is again cycled to move pistons 22 and die 24 to their extended position for stripping the formed blank 26 from the die 27. With the system as illustrated, it will be evident that the booster 14 can be cycled when desired to apply the desired cushion pressure to the die 24.

Alternatively, half of the cylinders 10 may be connected instead to a separate hydraulic circuit like that illustrated and controlled independently thereof so that all of the cylinders 10 will be subjected to booster pressure during part of the closing of the press ram and so that only half of such cylinders 10 will be subjected to booster pressure during another portion of the closing. This may be accomplished by appropriate setting of the cams 92 which control the cycling of the booster 14 of such separate hydraulic circuits. When using other dies for different requirements,'the booster may be cycled more than once during the closing of the press ram.

The upper die ring 29 is also backed up by a separate hydraulic cushion like that illustrated and which includes actuating cylinders 111 having pistons 122 normally subjected to relatively low tank pressure. The hydraulic cushion for the die ring 29 includes a hydraulic circuit having counterparts of that illustrated, the booster of such circuit being cycled by its own press operated switch so that booster pressure is maintained on the die ring 29 during closing of the press ram, or at such times as may be desired, depending upon the dies being used and the drawing operations being carried out, and alternatively half of the cylinders 111 may be connected instead to a separate hydraulic circuit as described in connection with the cylinders 10.

The valve 110 under the discharge pressure of the booster 14 when energized will block ports 48, 52 until A spool or sleeve valve member 110 the pressure of the trapped fluid in line 36 and cylinders 10 exceeds the discharge pressure of the booster when the pressure differential on the valve will shift valve 110 to open ports 48, 52 and close ports 102, 104.

In returning to its position as illustrated from the position where the ports 48, 52 are blocked, the spacing between the ports 52 and 102 and the axial length of the valve member 110 are such that the valve 110 will block the port 102 before opening the port 52. Closing or restriction of the port 102, if the booster 14 is energized and the pressure on the booster side of the valve 110 is higher than that on the press side, will cause the valve 110 to move toward opening the port 102. During the closing of the press ram the pressure to which the hydraulic fluid in the cylinders 10 is subjected by the retraction of the pistons 22 and the die 24 will suddenly raise the pressure in the line 36 and the

bores

46, 108 and 106 above the booster pressure, whereupon the valve 110 will shift to open the flow between the ports 48 and 52 and release the high pressure fluid into the bore 54 leading to the tank 12. The valve 110 and its bore are made and the port 52 is located so that when the valve 110 is positioned to block port 52, only a small amount of travel of valve 110 (about one-quarter of an inch) is required to open port 52 and release high pressure fluid to the line 38. The valve 16, when the booster 14 is energized, functions as a pressure relief valve to provide a high pressure resistance to the displacement of hydraulic fluid from the actuating cylinders 10 during the closing of the press ram. Instead of using a single directional valve 16, two or more of such valves 16 disposed in parallel fluid flow relation may be connected in like manner to the

lines

36, 38 and 44.

In practice where a single valve 16 is employed, the valve 110 can be about the size illustrated (about /4 inch in diameter), whereas a hydraulic pressure booster such as 14 when employed without directional valve 16, in order to develop a suitable high pressure resistance to displacement of hydraulic fluid from the cylinders 10 requires pistons of from 6 to 12 inches in diameter with a stroke of from 10 to 20 inches. The mass of the valve 110 is very small and the frictional resistance to movement of the valve 110 is very low so that it is sensitive to pressure differences across it and will instantly move to crack port 52 when the pressure rises in the cylinders 10 above booster pressure and release hydraulic fiuid to the line 38 leading to the tank 12. If check valve 107 is not used, the spring 112 alone will instantaneously shift valve 110 to open port 52 since both sides of valve 110 Would be exposed to the same pressure. In any event, a Very small amount of movement of valve 110 will suflice to open port 52 instantaneously when the pressure in cylinders 10 exceeds booster pressure and release hydraulic fluid through port 52 to tank 12, thus preventing buildup of undesirable high pressure in line 36 and permitting accurate control of pressure of the hydraulic fluid trapped in line 36 and cylinders 10 before valve 110 opens port 52.

In FIG. 3 where like parts are indicated by corresponding reference characters, the system is similar but differs in the following respects. The hydraulic pressure booster comprising cylinder 200 and plunger 202 is mounted on the bolster or other fixed part of the press so that a member 204 movable with the press ram as its closes will engage and move the plunger or piston 202 before the die 206 on the ram engages the work blank so as to discharge hydraulic fluid under high pressure from the cylinder 200 into line 210 to shift valve 212 to block port 214. Normally piston valve 212 is positioned as illustrated by spring 218 with respect to

ports

214 and 216 so that hydraulic fluid under tank pressure is supplied to the actuating cylinders 10 and pistons 22 to bias die 223 to its extended position. Line 210 communicates with bores 220 and 222 of directional valve 224 so that the hydraulic fluid discharged from

booster

200, 202 is applied to one face of piston 212 so as to shift it against the force of spring 218. The bore 220 communicates with the chamber of check valve 225. A hydraulic fluid line 226 interconnects line 38 and bore 228 whereby hydraulic fluid under tank pressure is supplied past check valve 225 and through bore 220 to the cylinder 200. A normally closed adjustable spring loaded pressure relief valve 230 is connected via bore 232 to bore 222 so as to relieve excess pressure in line 210. Thus bores 232 and 228 and valve 230 provide a pressure relief by-pass around valve 212.

The arrangement is such that valve 212 will be shifted to block port 214 before displacement of hydraulic fluid from the cylinders so that valve 212 will function as a pressure relief valve like valve 110 to create the desired resistance to displacement of hydraulic fluid from cylinders 10 and hence to retraction of die 223 during closing of the press ram. Check valve 225 and pressure relief valve 230 will trap the fluid discharged from cylinder 209 and maintain valve 212 in blocking relation to port 214 as the ram closes until the pressure on the spring side of valve 212 exceeds the setting of the valve 239, whereupon valve 212 will be retracted. The fluid displaced thereby will cause pressure relief valve 230 to open and bleed off the excess fluid trapped between cylinder 200 and valve 230. The valve 212 can be small like the valve 110 so that the fluid displaced by the retraction of valve 212 will be a small amount. While the stroke of the plunger 262 will be longer than that of the pistons 22, the diameter of the plunger 202 and cylinder 200 can be very small since it need discharge only an amount of oil equivalent to the displacement of piston 212 before the piston 22 begins its retraction during closing of the press ram. However, as plunger 202 will be actuated until the press ram reaches the bottom of its stroke, fluid will be discharged from cylinder 200 even as the valve 212 is being retracted, but such fluid will be bled off via the pressure relief valve 230 along with the fluid displaced by retraction of valve 212. The capacity of valve 230 can be very small.

After the closing of the press ram the valve 212 will leave port 214 exposed whereby tank pressure will react on pistons 22 for stripping purposes. If it is desired to release the back pressure created by valve 212 when blocking port 214, this may be accomplished by opening rotary valve 240 momentarily or longer during closing of the press ram. Rotary valve 240 is normally closed by spring 241 and is disposed in a by-pass 242 around pressure relief valve 230. The actuating arm 244 of valve 240 is positioned to be moved by a rotary cam 246 geared to move with the press ram whereby the hydraulic pressure in bore 222 and on the under face of piston valve 212 may be relieved as desired to momentarily or longer release the cushion pressure reacting on piston 22 during closing of the press ram at any desired part of the closing cycle. Valve 212, like the valve 110, need move only a small amount from its position blocking port 214 to partially open such port and relieve the excess pressure (above the setting of valve 23%) developed during closing of the press ram.

While I have illustrated and described preferred ern bodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In a crank type press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said piston reacts and associated with said piston so as to retract said piston upon closing of the press ram, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder having a one-way connection with said tank so as to be supplied with hydraulic fluid under tank pressure, a directional valve with a bore therein, ports in said bore in fluid flow communication with the high pressure cylinder, the actuating cylinder, and the supply tank, a spool rnovable in said valve bore to open or block fluid flow between some of said ports, means biasing said spool to one position so as to permit fluid flow between said ports leading to said actuating cylinder and to said tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure, said spool being movable to another position in response to the discharge of hydraulic fluid from the high pressure cylinder to block fluid flow between said last-mentioned ports to provide resistance to displacement of hydraulic fluid from said actuating cylinder during the closing of the press, said spool having a face exposed to the hydraulic fluid in said actuating cylinder whereby said spool is moved toward said one position to direct fluid from the actuating cylinder back to the low pressure supply tank when the pressure on the actuating cylinder side of said spool exceeds the pressure on the opposite side of said spool, and means for energizing said high pressure cylinder to effect the discharge of hydraulic fluid therefrom to shift said spool to said other position prior to the retraction of the actuating cylinder piston in response to the closing of the press ram.

2. Apparatus according to claim 1 wherein said means for energizing said high pressure cylinder comprises an air pressure operated booster.

3. Apparatus according to claim 1 wherein said high pressure cylinder is arranged to be actuated to discharge hydraulic fluid therefrom by the press ram during the closing thereof.

4. In a crank type press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said piston reacts and associated with said piston so as to retract said piston upon closing of the press ram, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder having a connection with said tank so as to be supplied with hydraulic fluid under tank pressure, a directional valve with a bore therein, ports in said bore in fluid flow communication with the high pressure cylinder, the actuating cylinder, and the supply tank, a spool movable in said valve bore to control the flow between said ports leading to said actuating cylinder and said tank, a spring biasing said spool so as to permit fluid flow between said ports leading to said actuating cylinder and to said tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure, said spool being exposed to and movable in response to the discharge of hydraulic fluid from the high pressure cylinder to block fluid flow between said last-mentioned ports so as to trap fluid between said valve and said actuating cylinder, said spool being exposed to and movable in response to the discharge of hydraulic fluid from said actuating cylinder to permit fluid flow between said last-mentioned ports so as to direct the fluid from the actuating cylinder back to the low pressure supply tank, and means for energizing said high pressure cylinder to effect the discharge of hydraulic fluid therefrom to shift said spool to block fluid flow between said last-mentioned ports prior to the retraction of the actuating cylinder piston in response to the closing of the press ram.

5. Apparatus according to claim 4 wherein springs bias said die to its retracted position.

6. Apparatus according to claim 4 including a by-pass between said high pressure cylinder and said tank and around said directional valve, and a normally closed pressure relief valve in said by-pass.

7. In a crank type press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said cylinder and piston react, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder connected with said tank so as to be supplied with hydraulic fluid under tank pressure, a directional valve with a bore therein, four ports in said bore in fluid flow communication with the high pressure cylinder, the actuating cylinder, and the supply tank, a spool movable in said valve bore to open and close said ports, a spring biasing said spool so as to open two of said ports to permit fluid flow between said actuating cylinder and said tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure, said spool moving in response to the discharge of hydraulic fluid from the high pressure cylinder to close said last-mentioned ports and open two other ports in communication with said cylinders to permit fluid flow from said high pressure cylinder to said actuating cylinder, said spool being moved by hydraulic fluid discharged from said actuating cylinder when the high pressure cylinder is energized to direct the fluid from the actuating cylinder back to the low pressure supply tank, and means for energizing said high pressure cylinder to eflFect the discharge of hydraulic fluid therefrom.

8. In a crank type press, a hydraulic system for con trolling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said cylinder and piston react and associated with said piston so as to retract said piston upon closing of the press ram, a low pres sure supply tank with hydraulic fluid under low pressure, a high pressure cylinder connected with said tank so as to be supplied with hydraulic fluid, a directional valve with a bore therein, four ports in said bore, one of said ports being in fluid flow communication with the high pressure cylinder, two with the actuating cylinder, and one with the supply tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure and said die is biased to its extended position, a spool movable in said bore to open two of said ports while blocking the other two and vice versa, a spring biasing said spool to one position so as to block the two of said ports leading to said cylinders while said other ports are open, said spool being movable to another position in response to the discharge of hydraulic fluid from the high pressure cylinder to open said blocked ports and block said open ports so as to direct said high pressure fluid to the actuating cylinder, and being moved by the spring when the high pressure cylinder is deenergized to direct the fluid from the actuating cylinder back to thetank, and means for energizing said high pressure cylinder to eflect the discharge of hydraulic fluid therefrom so as to position said spool to block said ports leading to said actuating cylinder and said tank prior to the retraction of the actuating cylinder piston during the closing of the press ram.

9. In a press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pres sure, a die upon which said piston reacts and associated with said piston so as to retract said piston upon closing of the press, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder, a directional valve with a bore therein, ports in said bore in fluid flow communication with the actuating cylinder and the supply tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure and said die is biased to its extended position, a high pressure cylinder supplied with hydraulic fluid from said tank, a spool in said bore, a spring biasing said spool to a posi-. tion to open said ports, said spool being arranged to move in response to the discharge of hydraulic fluid from the high pressure cylinder to block fluid flow between said ports, and being movable from said blocking position by the hydraulic fluid displaced from said actuating cylinder when the high pressure cylinder is energized to direct the fluid from the actuating cylinder back to the low pressure supply tank, and means for energizing said high pressure cylinder to effect the discharge of hydraulic 8 fluid therefrom to shift said spool to block fluid flow between said ports prior to the retraction of said actuating cylinder piston during closing of the press.

10. In a press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said piston reacts and associated with said piston so as to retract said piston upon closing of the press, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder supplied with hydraulic fluid under tank pressure, a directional valve with a bore therein, four ports in said bore, one in fluid flow communication with the high pressure cylinder, two with the actuating cylinder, and one with the supply tank, a spool movable in said bore to open two of said ports when the others are blocked and vice versa, a spring biasing said spool so as to block the flow between said ports leading to said cylinders, said spool moving in response to the discharge of hydraulic fluid from the high pressure cylinder when energized to open said last-mentioned ports and direct said high pressure fluid to the actuating cylinder, and being moved by hydraulic fluid discharged from said actuating cylinder when the high pressure cylinder is energized to direct the fluid from the actuating cylinder back to the low pressure supply tank, and means for energizing said high pressure cylinder to effect the discharge of hydraulic fluid therefrom to said actuating cylinder when said piston is being retracted so as to provide a resistance substantially greater than tank pressure to the retraction of the piston in the actuating cylinder.

11. In a press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said cylinder and piston react and associated with said piston so as to retract said piston upon closing of the press ram, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder supplied with hydraulic fluid under tank pressure, a directional valve with a bore therein, ports in said bore in fluid flow communication with the actuating cylinder and the supply tank, a Valve member movable in said valve bore to open and close said ports, means biasing said valve member to one position to permit fluid flow between said actuating cylinder and said tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure, said valve member being movable to another position in response to the discharge of hydraulic fluid from the high pressure cylinder to block said last-mentioned ports so that said valve member provides resistance to displacement of hydraulic fluid from said actuating cylinder during the closing of the press, said valve member being movable in response to the discharge of hydraulic fluid from said actuating cylinder to direct the fluid from the actuating cylinder back to the low pressure supply tank when the pressure on the actuating cylinder side of said valve member exceeds the pressure on the opposit side of said valve member, and means for energizing said high pressure cylinder to effect the discharge of hydraulic fluid therefrom during the closing of the press to shift said valve member to block said ports prior to the retraction of said actuating cylinder piston, and a pressure relief by-pass between the dis charge side of said high pressure cylinder and said tank and around said directional valve 12. Apparatus according to claim 11 including a second by-pass between the discharge side of said high pressure cylinder and said tank and around said pressure relief by-pass and a valve in said second by-pass controlled by the press.

13. In a press, a hydraulic system for controlling a die thereof comprising a hydraulic circuit including an actuating cylinder and piston actuated by hydraulic fluid pressure, a die upon which said cylinder and piston react and associated with said piston so as to retract said piston upon closing of the press ram, a low pressure supply tank with hydraulic fluid under low pressure, a high pressure cylinder supplied with hydraulic fluid under tank pressure, a directional valve with a bore therein, ports in said bore in fluid flow communication with the actuating cylinder and the supply tank, a valve member movable in said valve bore to open or block fiuid flow between said ports, said ports when open permitting fluid flow between said actuating cylinder and said tank whereby said actuating cylinder is supplied with hydraulic fluid under tank pressure, said valve member moving in response to the discharge of hydraulic fluid from the high pressure cylinder to close said last-mentioned ports and in response to the discharge of hydraulic fluid from said actuating cylinder to permit fluid flow therebetween to direct the fluid from the actuating cylinder back to the References Cited by the Examiner UNITED STATES PATENTS 5/60 Danly 60-51 X 1/62 Williamson 60-51 JULIUS E. WEST, Primary Examiner.

Claims

1. IN A CRANK TYPE PRESS, A HYDRAULIC SYSTEM FOR CONTROLLING A DIE THEREOF COMPRISNG A HYDRAULIC CIRCUIT INCLUDING AN ACTUATING CYLINDER AND PISTON ACTUATED BY HYDRAULIC FLUID PRESSURE, A DIE UPON WHICH SAID PISTON REACTS AND ASSOCIATED WITH SAID PISTON SO AS TO RETRACT SAID PISTON UPON CLSOING OF THE PRESS RAM, A LOW PRESSURE SUPPLY TANK WITH HYDRAULIC FLUID UNDER LOW PRESSURE, A HIGH PRESSURE CYLINDER HAVING A ONE-WAY CONNECTION WITH SAID TANK SO AS TO BE SUPPLIED WITH HYDRAULIC FLUID UNDER TANK PRESSURE, A DIRECTIONAL VALVE WITH A BORE THEREIN, PORTS IN SAID BORE IN FLUID FLOW COMMUNICATION WITH THE HIGH PRESSURE CYLINDER, THE ACTUATING CYLINDER, AND THE SUPPLY TANK, A SPOOL MOVABLE IN SAID VALVE BORE TO OPEN OR BLOCK FLUID FLOW BETWEEN SOME OF SAID PORTS, MEANS BIASING SAID SPOOL TO ONE POSITION SO AS TO PERMIT FLUID FLOW BETWEEN SAID PORTS LEADING TO SAID ACTUATING CYLINDER AND TO SAID TANK WHEREBY SAID ACTUATING CYLINDER IS SUPPLIED WITH HYDRAULIC FLUID UNDER TANK PRESSURE, SAID SPOOL BEING MOVABLE TO ANOTHER POSITION IN RESPONSE TO THE DISCHARGE OF HYDRAULIC FLUID FROM THE HIGH PRESURE CYLINDER TO BLOCK FLUID FLOW BETWEEN SAID LAST-MENTIONED PORTS TO PROVIDE RESISTANCE TO DISPLACEMENT OF HYDRAULIC FLUID FROM SAID ACTUATING CYLINDER DURIN THE CLOSING OF THE PRESS, SAID SPOOL HAVING A FACE EXPOSED TO THE HYDRAULIC FLUID IN SAID ACTUATING CYLINDER WHEREBY SAID SPOOL IS MOVED TOWARD SAID ONE POSITION TO DIRECT FLUID FROM THE ACTUATING CYLINDER BACK TO THE LOW PRESSURE SUPPLY TANK WHEN THE PRESSURE ON THE ACTUATING CYLINDER SIDE OF SAID SPOOL EXCEEDS THE PRESSURE ON THE OPPOSITE SIDE OF SAID SPOOL, AND MEANS FOR ENERGIZING SAID HIGH PRESSURE CYLINDER TO EFFECT THE DISCHARGE OF HYDRAULIC FLUID THEREFROM TO SHIFT SAID SPOOL TO SAID OTHER POSITION PRIOR TO THE RETRACTION OF THE ACTUATING CYLINDER PISTON IN RESPONSE TO THE CLOSING OF THE PRESS RAM.